Creating Heavenly Karpatka Cake is a rewarding experience. Follow these simple steps to make this delightful dessert:

1. Preheat the Oven: Preheat your oven to 375°F (190°C).
2. Prepare the Pastry: In a saucepan, combine water, butter, sugar, and salt. Bring to a boil. Remove from heat and quickly stir in the flour until well combined.
3. Add Eggs: Allow the dough to cool slightly, then add the eggs one at a time, mixing well after each addition. The mixture should be smooth and glossy.
4. Spread the Dough: Divide the dough in half. Spread one half evenly onto a greased baking sheet to form the first layer.
5. Bake the Pastry: Bake in the preheated oven for about 20-25 minutes, until golden brown. Repeat the process with the second half of the dough for the second layer.
6. Prepare the Custard Filling: In a saucepan, combine milk, sugar, and cornstarch. In a separate bowl, whisk together egg yolks and vanilla. Gradually add the milk mixture to the yolks, stirring constantly.
7. Cook the Custard: Place the mixture back on the stove over medium heat. Stir constantly until it thickens. Once thickened, remove from heat and add butter. Stir until melted and smooth.
8. Assemble the Cake: Once the pastry layers have cooled, place one layer on a serving platter. Spread the custard filling evenly over the layer.
9. Top with Pastry: Place the second layer of pastry on top of the custard filling.
10. Dust with Powdered Sugar: Before serving, dust the top layer with powdered sugar for an elegant finish.

These steps will lead you to a beautifully crafted Heavenly Karpatka Cake that will surely impress!